复合材料加强薄壁铝梁吸能特性仿真与试验研究

发布时间：2018-03-05 23:29

本文选题：碳纤维复合材料　切入点：铝合金　出处：《湖南大学》2016年硕士论文　论文类型：学位论文

【摘要】：现阶段,汽车设计的目标是在满足安全性、舒适性的前提下,提高车辆的环境友好度。前者的趋势是更好的安全性能、舒适而多功能的组件,这些需求将增大整车的质量。后者的趋势是提高燃油效率和减少尾气排放,要求汽车轻量化。解决上述矛盾的重要途径是采用新结构和新材料。碳纤维增强复合材料因其良好的吸能特性而被用于汽车碰撞吸能。将碳纤维复合材料与薄壁金属梁结合,利用梁的渐进叠缩引导复合材料发生稳定失效,对汽车前纵梁等吸能部件设计有重要指导意义。本文基于外表包覆复合材料金属梁和内嵌蜂窝铝、塑料等材料金属梁的优良吸能特性,提出碳纤维复合材料层合板内芯加强薄壁铝梁新结构,通过仿真和试验方法,对梁结构吸能特性展开研究。首先,介绍单纯薄壁铝梁和复合材料层合板内芯的几何结构,测定碳纤维增强复合材料和铝合金材料力学性能。基于有限元软件,引入节点位移作为铝梁初始几何缺陷,采用改进的Hashin失效准则,开发用户子程序实现复合材料初始损伤判定及演化,建立了单纯薄壁铝梁和不同结构和厚度复合材料加强薄壁铝梁轴向冲击过程有限元模型。然后,针对仿真结果引入吸能量、比吸能及碰撞力效率等吸能特性指标评价,分析单纯薄壁铝梁和不同结构和厚度复合材料加强薄壁铝梁吸能特性,选取典型模型分析薄壁梁轴向压溃形态及载荷、能量随位移变化。通过能量变化阐述仿真结果可靠性并进行吸能特性总结。仿真结果显示,复合材料加强薄壁铝梁较单纯薄壁铝梁的吸能量和比吸能有显著提高。最后,根据仿真结果合理选择试验变量、制备试样,通过落锤装置开展轴向冲击试验。针对单纯薄壁铝梁,结合渐进叠缩形态和载荷-位移曲线分析其轴向压溃过程。针对复合材料加强薄壁铝梁,基于复合材料失效模式和载荷-位移曲线探讨复合材料对梁结构吸能特性的影响。通过吸能特性评价指标分析试验结果,对比梁结构仿真与试验压溃形态、载荷-位移曲线及吸能特性。在现有金属梁屈曲理论和复合材料极限强度理论的基础上,给出估算复合材料加强薄壁铝梁承载能力的经验公式。
[Abstract]:At present, the goal of automobile design is to improve the environmental friendliness of the vehicle on the premise of safety and comfort. The former trend is better safety performance, comfortable and multifunctional components. These demands will increase the quality of the vehicle. The latter trend is to increase fuel efficiency and reduce emissions. The important way to solve the above problem is to adopt new structure and materials. Carbon fiber reinforced composites are used in automobile impact energy absorption because of their good energy absorption characteristics. Carbon fiber composites are combined with thin wall metal beams. The stability failure of composite materials is induced by the progressive shrinkage of beams, which is of great significance for the design of energy absorption components such as front longitudinal beams of automobiles. This paper is based on the exterior coated metal beams of composite materials and aluminum honeycomb embedded in the composite materials. The excellent energy absorption characteristics of metal beams of plastics and other materials are discussed. A new structure of thin-walled aluminum beams reinforced with carbon fiber composite laminated plates is proposed. The energy absorption characteristics of the beams are studied by means of simulation and test methods. The geometric structure of the inner core of pure thin-walled aluminum beam and composite laminated plate is introduced. The mechanical properties of carbon fiber reinforced composite material and aluminum alloy material are measured. Based on the finite element software, the node displacement is introduced as the initial geometric defect of aluminum beam. Based on the improved Hashin failure criterion, a user subroutine is developed to determine and evolve the initial damage of composite materials. A finite element model for the axial impact process of pure thin-walled aluminum beams and composite reinforced thin-walled aluminum beams with different structures and thickness is established. The energy absorption characteristics of pure thin-walled aluminum beams and composite reinforced thin-walled aluminum beams with different structures and thickness are analyzed according to the energy absorption, specific energy absorption and impact force efficiency of the simulation results. The typical model is selected to analyze the axial crushing shape and load of thin-walled beam, and the energy varies with displacement. The reliability of simulation results and the energy absorption characteristics are described through energy variation. The simulation results show that, The energy absorption and specific energy absorption of composite reinforced thin-walled aluminum beams are significantly higher than that of pure thin-walled aluminum beams. Finally, according to the simulation results, the test variables are reasonably selected to prepare the samples. The axial impact test was carried out by the drop weight device. The axial crushing process of the pure thin-walled aluminum beam was analyzed in combination with the progressive folding shape and load-displacement curve. The composite reinforced thin-walled aluminum beam was strengthened. Based on the failure mode of composite material and load-displacement curve, the influence of composite material on the energy absorption characteristics of beam structure is discussed. Based on the buckling theory of metal beams and the ultimate strength theory of composite materials, an empirical formula for estimating the load-bearing capacity of composite reinforced thin-walled aluminum beams is presented.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U465

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